Source : Webster's Revised Unabridged Dictionary (1913)

Decay \De*cay"\, v. i. [imp. & p. p. {Decayed}; p. pr. & vb. n.
   {Decaying}.] [OF. decaeir, dechaer, decheoir, F. d['e]choir,
   to decline, fall, become less; L. de- + cadere to fall. See
   {Chance}.]
   To pass gradually from a sound, prosperous, or perfect state,
   to one of imperfection, adversity, or dissolution; to waste
   away; to decline; to fail; to become weak, corrupt, or
   disintegrated; to rot; to perish; as, a tree decays; fortunes
   decay; hopes decay.

         Ill fares the land, to hastening ills a prey, Where
         wealth accumulates and men decay.        --Goldsmith.

Decayed \De*cayed"\, a.
   Fallen, as to physical or social condition; affected with
   decay; rotten; as, decayed vegetation or vegetables; a
   decayed fortune or gentleman. -- {De*cay"ed*ness}, n.

Source : WordNet®

decayed
     adj 1: deteriorated by decay or rot; "decayed teeth"
     2: damaged by decay; hence unsound and useless; "rotten floor
        boards"; "rotted beams"; "a decayed foundation" [syn: {rotten},
         {rotted}]